An Optical Microscope Study of the Morphology of Xenon Hydrate Crystals: Exploring New Approaches to Cryopreservation

Alexey Kobelev,Nikolay Shvirst,Valery Yashin,Nikita Penkov,Mikhail Goltyaev,Eugeny Fesenko,Anatoliy Kovtun

doi:10.3390/cryst9040215

Abstract

One of the possible approaches to a new method of cryopreservation seems to be the controlled formation of a multitude of small crystals in an object, which, due to their size, will not damage cellular structures. Managing the crystal formation, given the stochastic nature of the process, is an extremely difficult task. Theoretically, it is simplified if there is a sufficient number of changeable physical parameters, affecting the process. From this point of view, the use of ice-like gas hydrates for the purposes of cryopreservation seems to be a promising option. We investigated the process of growth of xenon gas hydrates via standard microscopy under different conditions using the specialized optical cell for observation at elevated pressures. The formation of crystals was observed in the system “supercooled liquid–xenon–water vapor” at negative, near-zero and positive values of temperature, and pressure of xenon up to 8 atmospheres. The morphology of xenon hydrate crystals observed in the experiments was analyzed and classified into five categories. The influence of physical conditions on the predominant crystal morphology was also studied. We found no evidence that the possible damaging effect of hydrate crystals should be less severe than of ice crystals.

Highlights

Cryopreservation methods are widely used in science, medicine, agriculture, and biotechnology
A microscopic study of xenon hydrate morphology has been conducted for the first time
The morphology of crystals observed in the experiments was described and classified into five categories including the cubic, fine-grained, whisker, acircular and massive forms

Summary

Introduction

Cryopreservation methods are widely used in science, medicine, agriculture, and biotechnology. There is an active search for a new effective method of cryopreservation, which would allow the cryopreservation of large biological objects—large tissue volumes and organs. As a part of the search for new directions for the further development of cryopreservation technologies, the idea of using gas hydrates for cryopreservation was born in the late 60s [1]. Gas hydrates are ice-like substances, the crystalline framework of which are composed of water molecules linked to one another by hydrogen bonds. The guest molecules in gas hydrates should be 0.38–0.92 nm in diameter and can be represented by inert gas atoms, lower hydrocarbon molecules, Freon molecules and so on [2,3]. The inert gas atoms could be considered candidates for controlled formation of a multitude of small crystals in an object, which, due to their size

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